Thermostat



Allg. 30, 1932. L M PERSONS 1,874,117

THERMOSTAT Filed Jan. 9, 1930 IWI/6722507" Zazezce J 206350725 PatentedAug. 30, 1932 PATENT OFFICE LAURENCE I. PERSONS, Ol' ST. LOUIS, MISSOURITHERMOSTAT Application mea January s, isso. semi no. 419,584.

My invention relates to improvements in thermostats and has for oneobject to provide a new and improved form of an especially sensitivethermostat which will respond i readily to minute temperaturevariations. Another object is to provide a thermostat of small sizehaving the sensitivity usually associated with large sized thermostats.Another object is the provision of an improved, sensitive and efficientthermostat particularly adapted for use with control systems forheaters, oil burners and the like, althrough I do not wish to be limitedspecifically to such use. Other objects will appear 1l from time to timein the course of the specifcation and claims.

I illustrate my invention more or less diagrammatically in theaccompanying drawing2 whereinigure l is an elevation;

Figure 2 is a side'elevation with parts" in section;

Figure 3 is an elevation with the cover removed;

Figure 4 is a rear view;

Figure 5 is a detail; Figure 6 is a detail; and

Y Figure 7 is air elevation of the thermostatic member proper.

Like parts are indicated by like symbols throughout the specificationand drawin A indicates any suitable supporting ase and A1 is anadjusting shaft fixedly mounted on the base. Extending upwardly thenceis a control arm structure generally indicated as A2 which is of anysuitable electric insulating material. The arm A2 pivotally mountedonthe shaft A1, may be rotated in response to rotation of the settingfinger A with its indicating hand A4 aligned with the graduations of theexterior scale A6 upon the cover A, A7 indicates a slot throu h whichthe projection A4 outwardly projects, for manually setting rthe device.Any suitable connection may be made between the member A1 and the memberor lever A2 but I indicate a pin or projection A8 upon the member Azaligned with and penetrating a slot A in the recurved portion A1o of themember A, 5 which is pivoted as at A11 upon the base A.

Mounted upon the adjusting shaft A1 is any suitable thermo variableelement gen erally indicated as B, herein shown as coiled with one endof the coil penetrating a slot B1L in the end of the shaft A1. It willbe understood that the coil is made up of two sheets `of material havingdifferent co-eiicients of expansion, so that a change in temperaturecauses a movement of the coil, tending to move its upper end B2 eitherto the right or to the left as the case may be. Secured to the upper endBz of the coil B is an extension or leaf B11 of any suitable metaladapted to respond to a magnetic pull. It terminates in a contact memberB. It will be understood that the shaft A1, the coil B and the member Band the vContact member B1 are all electrically conductive. One end ofthe shaft A1 may serve or be provided with a binding post, as indicatedat B, whereby the conductor Ba may be secured thereto, which in turnextends to the binding post B". The opposite end of the binding post B7is connected to any suitable conductor B8, which forms part of thecontrol circuit adapted to be controlled by the thermostat.

Mounted upon the member A2 is a permanent magnet C, herein shown as ahorse shoe magnet. Itmay be clamped upon the member A for example by theholding late C1 and the screw C. Associated with t e plate C1 is aterminal C3 which is shown as in screwthreaded relation with the plate,as at C, to permit its adjustment. It is o posed to the terminal B4 u onthe leaf B. t will be understood that t e plate C1 and the terminal Care electrically conductive. They are connected'as bythe* conductor C'swith the bindin post Ce which in turn is in connection with vtheconductor C7 which forms part of the circuit desired to be controlled.

v.It will be observed, as in Figure 3, that counter-clockwise rotationof the lever A will move the contact Cs against the contact B. The armA, upon which the contact and magnet are mounted, is pivoted to theshaft A1. The opposite contact B1, being mounted on a flexible leaf, hasa movement the substantial equivalent it would have were it pivoted atabout the upper end Bz of the coil m B. In other words the effect is asif the two contacts were eccentrically pivoted. The result is that whenthe lever A3 is actuated to move the contacts together there is a slightsliding or wiping effect between the two contacts. This is sufficient tokeep the contacts clean, as this slight wiping effect takes place almostevery time the lever A3 is actuated.

Since the particular circuit and particular mechanism to be controlled'form no part of the present invention they are not indicated in detail.I have, however,shown the thermostat as adaptable for association withcontrol means for a heating member. For example, in controlling thecircuit for furnace dampers 0r draft controls or for oil burners, or forblower systems and air draft systems associated with furnaces I employ ahousing A5 with the slot A1 calibrated to indicate the desiredtemperature, or the temperature at which the control mechanism isexpected to go. Assume that the thermostat is employed with an electriccontrol circuit for an electrically operated oil burner, if the housetemperature is at and the pointer A4 is set at 75, the circuit will beclosed because the rotation of the arm A3 to put the pointer mid- `waybetween the figures 7 0 and 80. on the scale will move the permanentmagnet C so far to the left,.referring to Figure 3, that it will drawthe leaf B.3 and will thus oppose the contact B4 to the contact C3 andclose the actuating circuit above described and diagrammaticallysketched in Figure 7. When the termperature reaches the response to thethermostatic member B to the increase in temperature will be anunwinding of the coil and the shape and characteristics of thethermostatic element will be such that this unwinding will, when thehouse temperature of 75 is reached, be sufficient to withdraw the leafB3 and thus the contact B4, breaking the actuatingcircuit. On the otherhand, when the house temperature again drops below 75 the coil B willclose down and, when the i member B3 approaches the magnet C, the magnetwill exert its force and again close the circuit. The employment of themagnet provides a quick or snap action which reduces the lag or timenecessary for the closure of the circuit to take place. One or the otherof the contacts B4 or C3 may be made adjustable, and I have shown thecontact C3 as ad] ustable, in order to follow or adjust the closestapproach of the leaf Ba to the permanent magnet. This permits adjustmentof the greatest effective action of. the magnet upon the leaf B8 andpermits it to be set so that the magnet will not exert too powerful anattractive force to permit a prompt disengagement or circuit breaking inresponse to temperature changes.

It will be realized thatl whereas I have described and shown a practicaland operative device, nevertheless many changes might be made in thesize, shape, number and disposition of parts without departing from thespirit of my invention. I therefore wish my description and drawing tobe taken as in a broad sense illustrative and diagrammatic rather thanas limiting me to my specific showing.

I claim:

1. Ina thermostat, a base, a thermostatically responsive member mountedupon said base, including a portion responsive to magnetic attraction, amagnet, and means for adjusting its position toward and away fromnormally fixed in relation to said base and ay free end adapted to fiex.in response to variations in temperature, said upper end extendingsubstantially tangential to the outermost convolution of said coil andsaid magnet being opposed to said free end.

3. The structure of claim l characterized in that indicating means areassociated with the magnet support and are adapted for the setting ofsaid magnet to close said circuit at any desired temperature within thenormal range of control.

4. The structure of claim 1 characterized by the rovision of a pivotalconnection between t e magnet and the base, a temperature selectingfinger, and means for moving said magnet in response to movement of saidtemperatu re selecting finger.

5. In a thermostat, a base, a thermostatically responsive member mountedupon said base, one end of said member being secured to said base, theother being free to fiex in response to changes in temperature, a magnetmovably mounted upon said base, conductive contacts associated with thethermostat-ic member and the magnet, and arranged for make and break inresponse to fiexure of said free end, vmeans for adjusting said magnettoward or away from a free portion of the thermostatically responsivemember, a movable indicator element and a graduated scale opposedthereto said indicator element being interlocked with the movable magnetmounting and being adapted by its position along said scale, to indicatethe temperature at which the magnet will move the thermostatically'responsive member into circuit closing position.

6. In a thermostat, a base, a thermostatical- 1y responsive membermounted upon said base, including a portion responsive to magneticattraction, .a magnet movably mounted upon said base and means forvarying its position in relation to the magnetically responsive portionof the thermostatically responsive member, and conductive connectionsassociated with the magnet and the thermostatically responsive member,said connections and the thermostatically responsive member 'formingpart of a circuit controlled by the member, said connections formingpart of a circuit controlled by the thermostat, and means for moving themagnet to vary its position in relation to the magnetically responsiveportion of the thermostaticallyresponsive member, said means being atthe same time adapted to wipe one of the opposed contacts across theother.

8. In a thermostat, a base, a thermostatically responsive member mountedupon said base, including a bimetallic coil, the inner end of which issecured to the base, a generally tangential extension from the outer,free end of the coil, a contact mounted upon said extension, a contactopposed to said first mentioned contact, and a permanent magnet opposedto said extension, said permanent magnet and said second mentionedcontact being movably mounted upon said base for simultaneous adjustmenttoward and away from said extension.

9. In a thermostat, a base, a thermostatically responsive member mountedupon said base, including a bimetallic coil, the inner end of which issecured to the base, a generally tangential extension from the outer,free end of the coil, a contact mounted upon said eX- tension, a contactopposed to said irst mentioned contact, a movable support, a permanentmagnet opposed to said extension, said magnet and said second mentionedcontact being mounted upon said movable support, and means for adjustingsaid support, said Qontacts being adapted, when in conductive contact,to permit said extension closely to approach said magnet, while spacingit slightly away from the magnet.

10. In a thermostat, a base, a thermostatic member mounted thereon andincluding an extension of magnetic material, an arm pivotally mounted onthe base and carrying a permanent magnet disposed in opposition to saidmagnetic extension, cooperating contacts carried by the thermostaticmember and the pivoted arm, a second arm pivotally mounted on the base,said arms having interengaging features by which movement of the secondmentioned arm is communicated to the first mentioned arm to adjust themagnet and the contact carried by the rst mentioned arm with respect tothe thermostatic member.

Signed at St. Louis, State of Missouri, this 30th day of December, 1929.

LAURENCE M. PERSONS.

